The present invention relates to a method for switching data between appliances in a packet-oriented local area network and an external appliance connected to the local area network via a router.
In local area networks, such as “intranets” in companies, the individual users have normally extensive, shareable databases and applications available. Data are interchanged in the form of packets between the appliances connected to the local area network.
To route the packets within the local area network, two types of addresses are used, referred to in this case as the appliance address and the network address. The appliance address is firmly prescribed for an appliance by the manufacturer and cannot be altered. The network address is defined within the local area network and can be assigned to an appliance arbitrarily; e.g., by the network administrator. In a local IP network, the MAC address has the function of an appliance address, and the IP address has the function of a network address.
To allow a company's external employees, such as field staff or home workers, access to the intranet, it is desirable to be able to connect external appliances to the intranet which have the same options and access rights as are available to the appliances connected to it directly. A known approach to solving this problem is to define an additional network, referred to as a home network, in which a network address is assigned to the external appliance. A router in the local area network, which router can be connected to the home network, is provided with an entry which causes packets that are circulating in the local area network and are addressed to the home network to be received by the router and forwarded to the home network. However, this solution requires that an appropriate entry be made in the router for each external appliance which needs to communicate with the local area network.
Provided that the home network can be connected to the router, for example via a point-to-point (dialup) connection, this solution allows the external appliance to feed data packets into the local area network and to receive response packets relating to the data packets from appliances in the local area network. However, if an appliance in the local area network, as initiator of a connection, needs to send data to the external appliance, failure often occurs because, although the router has been informed of the home network address, the users or appliances in the local area network have not. If the external appliance is also occasionally operated with a direct connection to the local area network, such as in the case of an employee who sometimes uses a transportable computer in a company's building with direct access to the local area network there and sometimes uses it at home, then the additional problem arises that a user on an appliance in the local area network generally cannot know whether this employee or the computer currently can be reached at home or in the local area network.
If the connection between the local area network and the home network is not set up via a point-to-point connection, but rather via other packet-oriented networks, then another problem of this approach is that, for data packets to be forwarded correctly, an appropriate entry is necessary on every single router through which the data packet passes on the path between the local area network and the external appliance. Since these routers generally are not controlled by the operator of the local area network, the solution described above fails because of prohibitive administration complexity.
It is an object of the present invention, therefore, to specify a method for switching data between appliances in a packet-oriented local area network and an external appliance connected to the local area network via a router, and a router which is suitable for carrying out the method, which allow the external appliance to be connected to the local area network with minimal administration complexity.